This invention is directed toward supporting thin-walled containers such as bottles during a filling, capping or like operation, and more particularly toward improvements therein directed toward accommodating the effects of creep in such containers.
U.S. Pat. Nos. 3,812,646 and 3,831,344 disclose a method and apparatus for supporting lower body portions of thin-walled plastic containers against outward deflection and damage during application of a top load in conjunction with a filling, capping or like operation. It is well established as ecologically desirable to reuse such containers many times before eventually discarding them, yet it is also true that when such containers are used in pressure applications at wall thicknesses which are functional and competitive with glass and metal, creep in the thermoplastic material will occur which results in slight deformation of the walls because of exposure to such pressure of the contents. A certain amount of such creep is permanent in that such deformation remains after pressure release, and such permanent creep is necessarily reflected in the condition of the container on the occasion of each of the multiple refillings and recappings. Such creep in the base area where pressure is greatest is not always uniform. For example, a locally thin region tends to creep more than a thicker one with the result that the container leans slightly to one side when self-supporting on a flat surface. Also, an axial increase or growth in overall height can occur when the container has a pressure-resistant raised base extending partially up into the body which partially everts under the influence of pressure, or in other words is urged outwardly of the body interior. Combinations of such height increase in one region of the container periphery plus lean-producing bulge in another region can also occur to complicate attempts to accommodate one or the other of these phenomena.
Though these slight deformities produced by creep can generally be maintained at levels which do not affect performance characteristics or render the containers functionally unacceptable to a customer of the package, they nevertheless can cause serious problems during filling and capping. More specifically, when a rather substantial top load on the order of 20 to 180 or more kilograms is applied to such a container in connection with application of a pressure resistant closure to its open end, it is conventional, as disclosed in the above mentioned patents, to envelop the lower end of the container with a support cap to prevent collapse of such area due to the applied load. However, certain horizontal and vertical tolerance limits must be maintained between the container and the cooperating location of the filling and capping apparatus components in order for the latter to function successfully. Thus, if the container is too tall, it cannot be accommodated in the vertical space between the filling or closure-applying head of the apparatus and the support member for the base, whereas if the container is canted in its supported position due to the effect of uneven creep, such heads will not seat or cooperate evenly with the wall surface around the opening of the upper end of the container with the result that the latter will be crushed or otherwise damaged during the filling or closure-applying operation because of application of the top load to a surface which is too limited in area.